black canker vs shitskin

black canker

noun
  • Any of several plant diseases causing the formation of dark cankers. 

  • The larva of the turnip sawfly (Athalia rosae), an agricultural pest having the appearance of a black caterpillar. 

shitskin

noun
  • A person with dark-coloured skin. 

How often have the words black canker and shitskin occurred in a corpus of books? (source: Google Ngram Viewer )